[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Avian flight stroke origin
One of the reasons the dichotomy was thought to exist (and still does today)
was a mistaken assumption that arboreal and terrestrial launch in birds are
fundamentally different, which they are not. In fact, they are almost identical.
Sent from my iPhone
On Aug 11, 2011, at 3:42 AM, "Dr Ronald Orenstein" <email@example.com>
> This raises a point that I still do not understand. Why is it assumed that
> arboreality and terrestriality are such vastly different ways of life that
> entire lineages can be assumed to have been one or the other, when living
> birds, mammals, reptiles etc clearly show that this is not the case? In
> birds alone we have genera containing both highly arboreal and purely
> terrestrial species (eg Coracina, whose members are mostly arboreal but which
> includes the terrestrial Ground Cuckoo-Shrike C. maxima), families such as
> Corvidae with secondarily-terrestrial genera like Podoces, etc.
> It can be objected that these are much better fliers than maniraptorids, and
> that getting into a tree does not require special climbing adaptations if you
> can fly there. In that case, what about (say) squirrels, which range
> similarly from the ground to the treetops and include gliding species. If a
> marmot and a flying squirrel can be close relatives, why can't dromaeosaurids
> (say) have included a similar mixture?
> Further, as I have said here before, a number of birds, including
> particularly the cracids, can shift back and forth between trees and the
> ground with ease, and others feed on the ground and nest in trees (including
> such unlikely tree-dwellers as ducks). Could there have been tree- or
> cavity-nesting dinosaurs? We'd be unlikely to find fossil evidence on the
> Also, even flightless or near-flightless species of birds can get up into a
> tree without having climbing-adapted front limbs. It's quite amazing to see
> the ability some birds have of getting around in trees by simply jumping from
> branch to branch, and if the trees have limbs near the ground they can reach
> the canopy in this way too. A good example might be the Kokako (Callaeas
> cinerea) of New Zealand, which is a fairly weak flyer (and, oddly for a
> passerine, a folivore), but which is almost if not entirely arboreal; it
> tends to leap upwards and fly/glide downwards.
> Ronald Orenstein
> 1825 Shady Creek Court
> Mississauga, ON
> Canada L5L 3W2
> On 2011-08-11, at 1:36 AM, Tim Williams <firstname.lastname@example.org> wrote:
>> Jaime Headden <email@example.com> wrote:
>>> So close! From the title: "Assessing Arboreal Adaptations of Bird
>>> AVIAN antecedents. It would have been so beautiful!
>> It's not just the alliteration that falls short. I also found myself
>> disagreeing with quite a few of the conclusions in the paper.
>> Nevertheless, it's pleasing to see Dececchi & Larsson (2011) refute
>> the hypothesis that the ancestors of birds were specialized for
>> arboreality. That's always good to see, because this is the central
>> plank of the BANDit's scenario-driven approach to the evolution of
>> avian flight. Dececchi & Larsso single out the splayed, quadrupedal
>> posture of "four-winged" gliding theropods for special criticism.